Particulate emissions in the exhaust products of a variety of devices ranging from automobiles to steel mills frequently are a limiting factor in the usefulness of such devices because of environmental considerations. Apparatus for isolating and preventing particulate emissions from reaching the atmosphere are many and varied. One specific problem has been control of particulate emissions from an internal combustion engine such as a diesel engine. Due to their higher efficiency, diesel engines have frequently been considered as one way to alleviate gasoline fuel shortages. Diesel gas pollutant emissions have been reduced to an acceptable level; however particulate emissions which are more severe in a diesel engine than in a gasoline engine still have not been reduced sufficiently from an environmental point of view. Diesel engines currently utilized for automobiles produce up to two grams of particulates per mile of opration. This number has to be reduced substantially in order for the automobile diesel engine to become a truly acceptable alternative to the gasoline engine.
Considerable automotive industry efforts are being undertaken to solve this problem. Several approaches are being considered which include: (1) modifying engine design to reduce particulate formation, (2) adding chemicals to fuel to suppress particulate formation, and (3) filtering the particulates using in-situ catalysts at the engine exhaust temperature which is about 330.degree. F. To data none of these approaches have been very successful. Approach (1) is difficult because the combustion process in a diesel is not well understood. Approach (2) is not highly desirable because additives may generate additional pollutants and induce engine deposits. Approach (3) is not yet satisfactory because diesel exhaust tempeatures are too low for an efficient catalytic reaction, and conventional filtering of the particulates presents a maintenance problem in that approximately one gallon of particulates is generated each one thousand miles. Use of heating elements for heating the diesel particulates until they oxidize has been found to be energy inefficient and introduces difficult engineering design problems.
The present invention solves the above problems by providing an apparatus and method for destructively removing particles from the diesel exhaust by vaporizing the particulates so that they combine with oxygen to form carbon dioxide.